WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC
SEC Form 13F institutional filer · CIK 0001644956
13F-HR · 96 reported holdings · 2026-03-31
William Blair Investment Management, LLC is an asset manager.
Reported long-US-equity value
$12.10B
Top-10 concentration
63.1%
WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC — $12.1B AUM allocation strategy
WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC files SEC Form 13F and reports $12.1B of long US equity value across 96 reported holdings for 2026-03-31.
Its largest sector bet is Information Technology 46.3%, followed by Communication Services 10.7% and Consumer Discretionary 7.1%.
The top 10 holdings account for 63% of reported value — a conviction-weighted book concentrated in its best ideas. The sector and industry splits below are of the same reported value. Track quarter-over-quarter adds, trims, new positions and exits below — sourced from SEC 13F filings, public domain.
WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC — latest SEC 13F insights
Reported long-US-equity value (13F AUM)
$12.1B
total across 96 reported holdings · 2026-03-31 · excludes shorts, cash, non-US
Top-10 concentration
63% of value
higher = narrower conviction; lower = spread / hedging
Biggest adds (shares)
+$CHRW +604K sh · +$103M+$CMG +598K sh · +$2.6M+$NOW +223K sh · −$81.2M
Biggest trims (shares)
−$NVDA −1.69M sh · −$423M−$AMZN −1.22M sh · −$354M−$ORCL −1.2M sh · −$237M
Sector allocation (share of reported value)
each slice is a share of the reported long-US-equity value — smaller sectors and the rest of the book roll into “Other holdings”
Qtr shift = share-point change vs the prior quarter's filing — first period tracked for this filer; the column fills in with the next quarterly refresh.
Industry allocation (share of reported value)
- Semiconductors20.3%—
- Systems Software10.9%—
- Interactive Media & Services10.7%—
- Technology Hardware, Storage & Peripherals10.1%—
- Broadline Retail5.5%—
- Transaction & Payment Processing Services4.4%—
- Industrial Gases2.6%—
- Consumer Staples Merchandise Retail2.5%—
- Other holdings32.9%—
the finer GICS cut of the same book — same denominator — smaller industries roll into “Other holdings”
Qtr shift = share-point change vs the prior quarter's filing — first period tracked for this filer; the column fills in with the next quarterly refresh.
Top S&P 500 holdings
10 of 10 rows · sorted by Value ↓
| Ticker | Holding | Shares | Value | Δ QoQ | Weight |
|---|---|---|---|---|---|
| $NVDA | NVIDIA Corporation | 8.94M | $1.56B | -1.69M | 12.9% |
| $AAPL | Apple Inc | 4.81M | $1.22B | -632K | 10.1% |
| $MSFT | Microsoft Corporation | 2.9M | $1.07B | -594K | 8.9% |
| $GOOG | Alphabet Inc. Class C Capital Stock | 2.5M | $720M | -650K | 6.0% |
| $AVGO | Broadcom Inc | 2.2M | $681M | -335K | 5.6% |
| $AMZN | Amazon.com Inc | 3.16M | $659M | -1.22M | 5.4% |
| $META | Meta Platforms Inc | 1.01M | $580M | -174K | 4.8% |
| $MA | Mastercard Incorporated | 1.06M | $530M | -24.3K | 4.4% |
| $LIN | Linde plc | 636K | $315M | -7.13K | 2.6% |
| $COST | Costco Wholesale Corporation | 302K | $301M | -26K | 2.5% |
…and 86 more holdings in the full 13F filing (top positions only shown).
SEC Form 13F data sets · public domain · 45-day filing lag · >$100M AUM managers · as reported
← All 13F filers·← QuantOrb.pro
How to read Δ QoQ — the five insight categories, and the caveats
The categories. Analysts, quants and retail traders look past total portfolio value to isolate actionable signals. Five categories matter.
Conviction & concentration shifts
New positions vs complete exits — a brand-new stock signals high conviction; a full liquidation suggests a broken thesis or tax-loss harvesting. Aggressive sizing — look at share count, not dollars: a 20% share increase during a drawdown is strong dip-buying. Concentration — a narrowing top-5/10 means conviction; spreading capital across more names means hedging.
Sector & macro allocation rotations
Aggregating Δ QoQ moves across sectors shows where smart money is leaning in or sneaking out — rotating out of growth into defensives or energy, for example. The fund's total long equity exposure quarter-over-quarter is a proxy for overall institutional risk appetite.
Crowding & smart-money consensus
When several managers initiate or expand the same stock in the same quarter, that is institutional consensus. Contrarian reads: top pickers buying hard into a beaten-down name the market is selling.
Derivative & option overlays
Reported call/put changes indicate whether managers are adding downside hedges or leveraging upside exposure. Note: a long increase may be half of a market-neutral pair trade.
Who reads this
| Retail "cloners" | High-conviction ideas to replicate ~45 days after quarter-end. |
| Corporate IR | Which funds bought or dumped the stock, before the next call. |
| Quant / algo traders | Cross-sectional factor inputs: flow, momentum, ownership. |
Four caveats before you trade on it
- 45-day lag — holdings are quarter-end; positions may already be closed.
- Long-only — 13Fs miss shorts, pair trades and cash.
- No non-US / fixed income — the picture is US equities plus options.
- Corporate actions — splits and spinoffs distort raw share deltas.
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